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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

OLIVE OIL

407

of the fatty acids and the saponification number and raises the Maumene
number and refractometric value of olive oil.

3.  COTTONSEED OIL : by the reactions of Halphen and Milliau (modified
by Armani and by Tortelli and Ruggeri) (see Cottonseed Oil).   Further
it raises the specific gravity, the melting and solidifying points of the fatty
acids, the Maumene number, the refractometric value and the iodine number.

4.  SESAME OIL :   by the Villavecchia and Fabris reaction (see Sesame
Oil) ; it alters the different characters in the same sense as does cottonseed
oil.

5.  OTHER SEED OILS IN GENERAL :   by the general colour reactions
already indicated (see e, above) and by certain alterations in the characters
of the oil.                                                           ;

6.  ANIMAL OILS : by the smell and by testing for cholesterol as indicated
for tallow (olive oil scarcely contains traces of phytosterol).   Fish oils and
oils of other marine animals are detected by the Tortelli and Jaffe reaction
(see Fish Oils).

7.  MINERAL OILS :   by the lowering of the saponification number and
by examination of the unsaponifiable part (see General Methods, 19).

3. Detection of Sulphocarbon Oil.—200 grams of the oil are
vigorously shaken with 50 c.c. of 90% alcohol and distilled from a water-
bath, the distillate being collected in a flask containing a few c.c. of alcoholic
caustic potash solution (r : 10) (recently prepared from the purest alcohol)
and immersed in cold water. When about two-thirds of the alcohol added
to the oil are collected, the distillation is interrupted. The distillate is
faintly acidified with dilute acetic acid and treated with 1-2 drops of dilute
copper sulphate solution: in presence of potassium xanthate (formed by
the action of the carbon disulphide, distilled with alcohol, on the alcoholic
potash), a brown coloration is formed and then a yellow precipitate of
copper xanthate.1 The presence of carbon disulphide in the oil is hence

concluded.

*
* *

Genuine comestible olive oil should have the following characters :

It should be clear and have the normal odour and taste.

Solidifying •point; it should begin to become turbid at about 10°, and as
a rule it sets to a semi-solid mass between 6° and 2° ; at o° it forms a soft solid.

Melting point of the fatty acids:   22-28°.

Solidifying point of the fatty acids:   24-21 °.

Specific gravity at 15°:  0-914-0-919.

Reading on Zeiss butyro-refractometer at 25° : 62-63. With oils which are
defective or altered, or obtained from bad olives, or washed or extracted with
carbon disulphide, the reading may be as low as 60.

Maumene number (Tortelli) : 41-47° (44° may be taken as the mean). With
the Jean thermo-oleometer : 32-39°.

A cid number:   2 at the most.

Saponification number:   185-196 (normally 192-195).

*   Iodine number :   79-88.   Most commonly the iodine number is 80-83, only
Certain oils from Liguria and Spain, and more often the oils of Crete, Tunis,

1 Well refined sulphocarbon oils and those heated for an hour at 130° no longer
give the above reaction or any other reaction specific for carbon disulphide or other
sulphur compound.°~'nd chemical characters are given in